But an injury has forced Grant out of yet another title shot. Grant was supposed to face Henderson at 164, but withdrew from the fight after suffering a concussion during training. Pettis, who suffered an MCL tear in June, recovered quicker than expected and replaced Grant. He submitted Henderson in the first round to win the title.

Grant confirmed that he would not be fighting Pettis on Twitter Monday.

“Unfortunately I won’t be fighting Pettis on Dec. 14. I am still not yet 100 percent and can’t commit to fight. The UFC is going with someone else instead,” the 29-year-old wrote. “It sucks, but it is the best for both myself and the UFC. Please don’t worry. I’ll be back, and if I gotta fight someone else to get back to where I wanna be, then that’s what I’m gonna do. I’m not bitter.”

The UFC announced on Monday night’s Fox Sports Live that Josh Thomson would be Anthony Pettis’ first challenger. The 34-year-old is coming off a TKO victory against Nate Diaz at UFC on Fox: Henderson vs. Melendez in April. Thomson earned Knockout of the Night for the win.

Thomson made his UFC debut at UFC 44 in September 2003, knocking out Gerald Strebendt in the first round. He fought two more times in the promotion before switching to Pride and then Strikeforce. He made his Strikeforce debut in March 2006 against Clay Guida, but lost the match by unanimous decision. He wouldn’t come back to the UFC until almost a decade later.

Nine months later, Thomson defeated Nam Phan for the lightweight championship at Strikeforce: Triple Threat on December 8. He held on to the title for three years before losing it to Gilbert Melendez at Strikeforce: Evolution on December 19, 2009. He tried to win the title back at Strikeforce: Barnett vs. Cormier in May 2012, but lost by split decision.